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fix: support sparse storage with accumulators - #421
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Signed-off-by: Henry Schreiner <henryfs@princeton.edu>
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C++17 version, FWIW: auto [it, _] = map->try_emplace(idx, value_type{});
it->second += u; |
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Looks good, thanks. |
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Will this make it into 1.91? The deadline for fixes is April 1. (Doesn't have to) |
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Yeah, I think I can merge it into the release, because it is a bug-fix. |
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Add a hash-map backed `DoubleSparse` storage that only allocates filled cells, making histograms over very large or high-dimensional axis spaces feasible. Backed by `storage_adaptor<unordered_map<size_t, double>>`. Scoped to `double` only for now: accumulator-backed sparse storages need boostorg/histogram#421, which ships in Boost 1.92 (the repo vendors 1.90). Data access is COO-first and deliberately not a full drop-in: - `.view()` raises (no contiguous buffer to view into). - `Histogram.to_coo(flow=False)` returns the filled cells as `(per-axis index tuple, values)`, numpy-nonzero style. - The copying accessors `values()`/`variances()`/`counts()` and `np.asarray(h)` densify into a fresh array, so they keep working. - `at()` reads, slicing, projection, sum and histogram addition stay sparse. Serialization: pickle round-trips via free save/load on `double_sparse` (COO key/value arrays); UHI to_uhi/from_uhi store COO under a `"sparse"` payload plus writer_info, reconstructed via a C++ `_from_coo` bulk setter. Assisted-by: ClaudeCode:claude-opus-4.8
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@HDembinski Will this make it into 1.92? The deadline for all changes is August 5. (I've got a few other fixes open too, and I can submit a fix for #430 if you want me to). |
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yeah let's aim for that |
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@HDembinski Will this make it into 1.93? The deadline for new libraries is October 21, and breaking changes is October 28, and all changes is November 4. I assume it's easier before those deadlines to update. (I've got a few open PRs too, #429 should be ready for review). |
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This is a fix for #416. Added test fails without the fix, compiles and passes with the fix. This was blocking sparse storage in boost-histogram (can't promise it is the only blocker, but was the first one we hit).
Use copilot in VSCode, which selected GPT-5.3-Codex, to convert the issue into a fix and test.